1. Field of the Invention
The present invention relates to a light source unit including a plurality of light sources, alight source apparatus including the light source unit, and a projector including the light source apparatus.
2. Description of the Related Art
In these days, data projectors are used in many cases as image projection apparatuses which project screens or video images of personal computers and further images based on image data stored in memory cards on to a screen. These projectors are such that light emitted from a light source is concentrated on a micromirror device called a DMD (Digital Micromirror Device) or a liquid crystal plate for displaying a color image on to the screen.
In projectors of the type described above, conventionally, projectors using a high-intensity discharge lamp as a light source have been the mainstream of projectors. In recent years, however, there have been made many developments and proposals on light source units which use, as a light emitting device of a light source apparatus, a semiconductor light emitting device such as a light emitting diode (LED), a laser diode (LD) or an organic EL.
For example, Japanese Unexamined Patent Publication No. 2004-220015 proposes a light source apparatus in which light emitting devices are disposed in a matrix-like configuration so as to increase a quantity of light. However, in the invention described in the patent document, the light emitting area is increased, which increases the value of Etendue. Because of this, there is much light which becomes unnecessary or is not used, leading to a problem that the utilization efficiency of light emitted from the light emitting diodes is reduced. Note that Etendue is a value which represents the spatial expansion of effective light as a product of area and solid angle and which is preserved in the optical system.
Then, Japanese Unexamined Patent Publication No. 2004-341105 proposes a light source apparatus comprising a light emitting wheel in which fluorescent materials are disposed in a circumferential direction and an ultraviolet light emitting diode. In the proposal made in Japanese Unexamined Patent Publication No. 2004-341105, ultraviolet light is shone on to the light emitting wheel from a rear surface side thereof as excitation light, and fluorescent light emitted from a front surface side of the light emitting wheel is used as light source light.
In the invention described in Japanese Unexamined Patent Publication No. 2004-341105, in order to increase the quantity of fluorescent light, the output of the excitation light needs to be increased. Although there is a method for utilizing a plurality of ultraviolet light emitting diodes as a method for increasing the output of excitation light, as this occurs, since the number of bright points of the excitation light source is increased, there has been caused a problem that a large-scale light gathering lens becomes necessary to gather light beams emitted from the plurality of bright points to the fluorescent materials.